1. Field of the Invention
The present invention relates to apparatus for the treatment of metallic workpieces, and more particularly to apparatus used for the hardening of such metallic workpieces.
2. The Prior Art
It is known to subject metallic workpieces to various sequential treatments in order to harden them, such treatments including the subjecting of the workpieces to a glow treatment or ion-treatment (e.g., a plasma carburization), and to an oil bath treatment, and suitable apparatus for conducting such treatments are known. One known apparatus, made by the Ulvac company, includes a hollow furnace (located within a larger enclosed recipient which includes an entry and discharge station) which mounts a sealing door that can be opened to provide access to the treatment chamber therein, and which includes suitable heating elements and electrodes (the electrodes and their attached electrical lines being insulated from one another and from the other elements associated with the furnace), as well as evacuating and gas supply ducts, and a transport structure which can transport the metallic workpieces to be treated into the treatment chamber in the furnace, deposit the metallic workpieces on one of the electrodes, and then withdraw from the furnace, such that the door thereof can then be closed and the glow treatment (ion carburization, ion nitration, etc.) can be carried out. After such treatment the transport structure can be moved back into the furnace to pick up the still hot workpieces, and then transport them to other treatment stations, e.g., the oil bath treatment station.
With regard to the foregoing, the technology of ion carburization is well known and, for example, is discussed in detail in West German Patent No. 668,639. In order to ensure a stable glow discharge in a furnace, the two electrodes (anode and cathode) must be positioned so as to be electrically insulated from one another and all other components. Thus, as far as the prior art is aware, the transport structure used to transport the workpieces into the furnace must be removed prior to the operation of the furnace, and thus in the known prior art processes the transport structure leaves each workpiece, together with the plate on which it rests, in a charging pan in the furnace and then withdraws from the furnace prior to the actual operation of the furnace.
However, in order to achieve the necessary steps of transport of the workpiece to the furnace, deposit of the workpieces in the furnace, pick up of the workpieces after treatment and then removal of the treated workpieces from the furnace, the prior art transport structures have been very expensive, not only because they must include numerous independently movable elements, complex control systems and an overall regulator, but because they must be extremely durable so as to avoid the need for human assistance in their operation. Furthermore, operations using these transport structures are inefficient since such transport structures consume much time in accomplishing their deposit and pick up operations, and also a rapid quenching of the workpieces after the furnace has been opened can be only conditionally achieved.
It is thus an object of the present invention to overcome the drawbacks of the known hardening apparatus and to provide an apparatus for such purpose which is simple in construction and operation.